Introduction to genetics: Difference between revisions

Revision as of 18:25, 15 June 2022

Revision as of 20:25, 2 July 2022

Line 26:

Now imagine that this woman grows up and has children with a brown-haired man who also has a Bb genotype. Her eggs will be a mixture of two types, one sort containing the B allele, and one sort the b allele. Similarly, her partner will produce a mix of two types of sperm containing one or the other of these two alleles. When the transmitted genes are joined up in their offspring, these children have a chance of getting either brown or red hair, since they could get a genotype of BB = brown hair, Bb = brown hair or bb = red hair. In this generation, there is, therefore, a chance of the recessive allele showing itself in the phenotype of the children—some of them may have red hair like their grandfather.<ref name=OMIM/>

Many traits are inherited in a more complicated way than the example above. This can happen when there are several genes involved, each contributing a small part to the end result. Tall people tend to have tall children because their children get a package of many alleles that each contribute a bit to how much they grow. However, there are not clear groups of "short people" and "tall people", like there are groups of people with brown or red hair. This is because of the large number of genes involved; this makes the trait very variable and people are of many different heights.<ref>[http://www.childrensnyp.org/mschony/P02134.html Multifactorial Inheritance] Health Library, Morgan Stanley Children's Hospital, Accessed 20 May 2008</ref> Despite a common misconception, the green/blue eye traits are also inherited in this complex inheritance model.<ref name=Athro>[http://www.athro.com/evo/gen/inherit1.html#uncertainty Eye color is more complex than two genes], Athro Limited, Accessed 27 November 2010</ref> Inheritance can also be complicated when the trait depends on the interaction between genetics and environment. For example, malnutrition does not change traits like eye color, but can stunt growth.<ref>{{cite web |url=http://www.med.umich.edu/opm/newspage/2003/kidheight.htm |title=Low income kids' height doesn't measure up by age 1 |publisher=University of Michigan Health System |access-date=May 20, 2008 |url-status=dead |archive-url=https://web.archive.org/web/20080526034018/http://www.med.umich.edu/opm/newspage/2003/kidheight.htm |archive-date=26 May 2008 |df=dmy-all }}</ref>

==How genes work==

Line 69:

==Genetic engineering==

{{main|Genetic engineering}}

Since traits come from the genes in a cell, putting a new piece of DNA into a cell can produce a new trait. This is how [[genetic engineering]] works. For example, rice can be given genes from a maize and a soil bacteria so the rice produces [[beta-carotene]], which the body converts to vitamin A.<ref>Staff [http://www.goldenrice.org/ Golden Rice Project] Retrieved 5 November 2012</ref> This can help children suffering fromwith Vitamin A deficiency. Another gene being put into some crops comes from the bacterium ''[[Bacillus thuringiensis]]''; the gene makes a protein that is an [[insecticide]]. The insecticide kills insects that eat the plants but is harmless to people.<ref>[http://ars.usda.gov/is/ar/archive/nov99/pest1199.htm Tifton, Georgia: A Peanut Pest Showdown] USDA, accessed 16 May 2008</ref> In these plants, the new genes are put into the plant before it is grown, so the genes are in every part of the plant, including its seeds.<ref>[http://www.gmo-safety.eu/basic-info/129.bacterial-arsenal-combat-chewing-insects.html Genetic engineering: Bacterial arsenal to combat chewing insects] {{Webarchive|url=https://web.archive.org/web/20110515134013/http://www.gmo-safety.eu/basic-info/129.bacterial-arsenal-combat-chewing-insects.html |date=15 May 2011 }} GMO Safety, Jul 2010</ref> The plant's offspring inherit the new genes, which has led to concern about the spread of new traits into wild plants.<ref>[http://www.geo-pie.cornell.edu/gmo.html Genetically engineered organisms public issues education] Cornell University, Accessed 16 May 2008</ref>

The kind of technology used in genetic engineering is also being developed to treat people with [[genetic disorder]]s in an experimental medical technique called [[gene therapy]].<ref>{{cite web| last = Staff|date= November 18, 2005| url = http://www.ornl.gov/sci/techresources/Human_Genome/medicine/genetherapy.shtml| title = Gene Therapy| format = FAQ| work = Human Genome Project Information| publisher = [[Oak Ridge National Laboratory]]| access-date = 2006-05-28}}</ref> However, here the new, properly working gene is put in targeted cells, not altering the chance of future children inheriting the disease causing alleles.

Line 99:

{{Introductory science articles}}

{{Gene expression}}

{{DEFAULTSORT:Genetics, Introduction to}}